Dredging apparatus

ABSTRACT

A dredging apparatus for the removal of cuttings gathered around a bore hole mouth on the seabed has an ejector coupled to a suction hose and a conveyor pipe, respectively, for moving the cuttings to another place on the seabed. The dredging apparatus comprises a drive motor, a pumping device and an ejector, the drive motor being adapted to drive the pumping device which, in turn, is adapted to deliver a forced flow of water to the ejector in order to establish and maintain the ejecting effect. The ejector, pumping device and drive motor are assembled to form a unit. A cable delivers energy to the motor from the surface.

The present invention relates to a dredging apparatus, particularlyintended for the removal of cuttings at the seabed around bore holes,said apparatus comprising a suction hose assigned a driven ejectorwhich, at the ejecting aperture thereof, is coupled to an elongate pipewherethrough cuttings sucked in through the intake opening of thesuction hose are conveyed, said cuttings being conveyed through thesuction hose to the ejecting aperture of the ejector, where saidelongate pipe takes over the cuttings transport, feeding the cuttingsout through the discharge aperture thereof situated at a substantialdistance from the intake opening of the suction hose.

According to known technique, the ejector acting as the water flow basedconveyor of the dredging apparatus, is driven by a motor-operatedpumping device. When carrying out dredging and similar operations on theseabed, said pump is, according to known technique, mounted on theplatfrom deck and, from the pump, a coarse-dimensioned hose extends downto the ejector on the seabed. At sea depths of e.g. 150 meters or more,operations must be carried out using a substantial pumping pressure atplatform deck level, because one has to expect significant pressurelosses within the hose/pipe system down to the ejector.

According to prior art technique, water to the motor-driven water pumpis first pumped up to the platform deck and, thereafter, downwards againwithin the e.g. 150 meters long pipeline. Through the pipeline, e.g.300-400 m³ water per hour may be conveyed. Thus, the part of a knowndredging apparatus which is mounted on the deck constitutes adisproportionately large, bulky and heavy equipment package.

The ejector of the dredging apparatus working on the seabed is,preferably, assisted by a remote control vehicle (RCV) which may beadapted to guide the intake opening of the suction hose in order to holdit in a correctly positioned and orientated position in relation to theheap of cuttings.

The main object of the present invention has been to provide a space andweight saving dredging apparatus of the kind defined introductorily, inwhich also substantial energy savings are achieved.

According to the invention, this main object is realized by means of adredging apparatus designed, shaped and adapted in accordance with thecharacterizing clause of the following claim 1.

In accordance with the present invention, the ejector and its water pumpwith drive motor are built together to a unit lowerable down to theseabed, where to the intake end of the ejector, as known per se, iscoupled a suction hose/pipe for sucking in cuttings, mud, etc., desiredto be removed from a certain, first place on the seabed, e.g. around theupper mouth of a bore hole, and where to the pressure end of theejector, as known per se, is coupled a carrying off pipeline for thetransfer of sucked-in cuttings, mud, etc., to another place on theseabed, well spaced from said first place, power (electricity/hydraulicpressure) to the drive motor of the water pump being delivered through acable/hose from the surface/platform.

Through an arrangement according to the invention, significant weightsavings are achieved, neither pump aggregate nor water hose drum beingneeded on the platfrom deck. Also, the arrangement will result in verysignificant energy savings due to the very much reduced pumping lengthfor the drive water.

A dredging apparatus having an associated lowering and power supplyingcable according to the invention is further explained in the following,reference being made to a non-restricting examplary embodimentdiagrammatically illustrated in the accompanying drawings, in which:

FIG. 1 is a situational view showing the positioning of a dredgingapparatus according to the invention on the seabed, said dredgingapparatus having a hoisting wire and electrical cable connection to adrilling rig which has been shown on a substantially smaller scale thanthe dredging apparatus, and where the dredging by means of theejector-operated dredging apparatus is assisted by a RCV of anembodiment known per se and adapted to keep the intake opening of thesuction hose correctly positioned in relation to a heap of cuttingsaround a bore hole mouth;

FIG. 2 shows a detailed view of the dredging apparatus in a sideelevational view and on a significantly larger scale than in FIG. 1, cutthrough in a portion where a pipe bend having a narrowed outlet, fromthe pumping section of the dredging apparatus is passed down into theejector's pressure portion, which widens itself conically in the flowingdirection of the "mud", and to which is connected the upstream suckingportion of the ejector, said bend from the pumping section constitutinga part of the ejector, which directs an axially extending water jetmoving with a large speed towards the outlet opening of the connectedpipe, so that a suction effect is established in the connected hose,upstream of the outlet opening of the bend.

First, reference is made to FIG. 1 where, from a drilling platformhaving a rig 10, a drill pipe string 12 extends to a bore hole in theseabed formation 14, and where a template is indicated at 16. Around thebore hole mouth at seabed level, cuttings 18 have gathered in a heap.

The dredging apparatus according to the invention is, of course, notlimited to the nature of "the mud material". Any mud-like, sand, gravelor pebble-shaped materiale desired to be removed from one place at theseabed to another place thereron, may be conveyed therebetween inaccordance with the invention.

The dredging apparatus requires only the presence of an electricalgenerator or a hydraulic pump to deliver energy through a cable 20extending from the platform 10 to the drive motor of the dredgingapparatus. In this case, said drive motor is an electrical motor 22,FIG. 2, the dredging apparatus in general being denoted at referencenumeral 24.

In FIG. 1, reference numeral 26 denotes a remote control vehicle, knownper se, operating a tool 28 in the form of a grip, with which the tool28 can catch and hold the suction hose end 32' of the dredging apparatus24, the opposite end of the suction hose 32 is coupled to the suctionend of an ejector 30, and to the pressure end of the ejector, anelongate pipe or hose 34 is coupled, the length and, thus, the outletend thereof enabling a transfer of cuttings 18 from the area around thebore hole mouth to a discharge place 36.

In FIG. 2, the dredging apparatus 24 comprises a pumping device 38driven by the electrical motor 22. This pumping device has water intakeopenings 38', and the pressure end thereof is coupled to a 180° pipebend 40, the narrowing outlet end opening 40' thereof being passedwater-tightly down through and into an upstream section 30' of theejector's 30 flowing pipe portion, the outlet end of the pipe bend 40being directed in the water flowing direction through the ejector,constituting a part of the same, namely its part 40 which is coupled tothe water pump and which, through the pump device 38, establishes thedesired ejecting effect in the form of a directional water jet flowthrough the tubular flow portion 30', 30" and 30'" of the ejector. Tothe suction end of the ejector pipe 30, at the upstream end of thesection 30', a suction hose 32 is connected. The extent of the suctionhose 32 is indicated in FIG. 1, the outer, free intake end thereofhaving a funnel-haped inlet portion 32', through which cuttings 18 aresucked in and conveyed in a direction towards the ejector 30 in thesuction hose 32. At the outlet end opening 40' of the pipe bend 40, theejector 30 takes over the transport of the cuttings 18 and delivers themat the discharge opening of the ejector 30, at the flange coupling 42,where the pipe 34 forwards the transfer of the cuttings 18 to thepreviously mentioned place 36 on the seabed 14, at the discharge end ofthe pipe 34.

The electrical motor 22 to which the electrical cable 20 is coupled, maybe pressure-compensated.

The drive motor 22, pumping device 38, ejector 30,40 and, possibly, hose32 and pipeline 34 coupled thereto of the dredging apparatus may bedisposed within a frame 44 having an upper, central suspension ring 46,with which the frame 44 together with the dredging apparatus 24 may behoisted up and lowered down by means of a wire 48 operated from thesurface/the platform 10.

Suspension brackets 50 and supports 52 keep the individual components ofthe dredging apparat in their correct positions in relation to the frame44 carrying the brackets, supports, etc., for the mounting of thedredging apparatus.

Contrary to the known dredging apparatus of the kind concerned, wherethe pumping device and the drive motor thereof are disposed on theplatform deck and first have to pump water up from the surface of thesea, and where to the ejector 30,40 on the seabed extends a veryelongate water pipeline, e.g. of a length of e.g. 150 meters,corresponding to the distance from the surface down to the seabed 14,the ejector 30,40 of the present invention is assembled with the waterpump 38 and the drive motor 22 of the latter.

As no pressure drop occurs in the pipeline between the pumping device 38and the ejector 30,40 of a dredging apparatus according to theinvention, a pump and a drive motor each having a significantly smallercapacity than those used in prior art dredging apparatus may be usedwith the invention, simultaneously as the dredging apparatus releasesdeck space as drive motor and pumping device are positioned on theseabed together with the ejctor 30,40. Along with space savings on thedrilling platform, a significant weight reduction is achieved also.

What is claimed is:
 1. A dredging apparatus for performing work on aseabed, said dredging apparatus comprising:a drive motor; a pumpingdevice; an ejector having a pipe bend portion with a first end connectedto an outlet of said pumping device and a second narrowed outlet endforming a nozzle and passing down and into a pressure portion of saidejector, wherein said drive motor operates the pumping device and saidpumping device delivers a forced water flow to said pressure portion ofsaid ejector to maintain an axially extending waterjet towards an outletend of said ejector; a suction pipe connected to an inlet end of saidejector, upstream of said pressure portion of said ejector, said suctionpipe having an inlet portion for sucking in materials on the seabed,wherein said materials are sucked into said pressure portion of saidejector upstream of said axially extending waterjet; an outlet transferpipe connected to said outlet end of said ejector, wherein said suctionpipe, said ejector pressure portion and said outlet transfer pipe form acontinuous bore for transferring materials from one location on a seabedto a second location and, wherein said ejector, the pumping device, andthe drive motor form an integral unit.
 2. A dredging apparatus as setforth in claim 1, wherein the unit is suspended from a frame, the drivemotor and the pumping device are disposed in a prolongation spatialrelationship to each other at an upper level within the frame, theejector is disposed below said drive motor and the pumping device at alower level of the frame, wherein the pumping device, and an oppositeend of the motor, are connected to an upstream end of said pipe bendportion, said pipe bend portion constituting a 180° bend, and whereinthe downstream end of said pipe bend portion is positioned between saidejector pipe's suction end and said ejector outlet end, with the outletthereof facing the ejector opening of the ejector pipe and said outlettransfer pipe, wherein the ejector has a gradually increasing pipediameter in a direction from the pressure portion of the ejector to theoutlet end of the ejector.
 3. A dredging apparatus as set forth in claim1, wherein the drive motor includes one of an electrical motor and ahydraulic motor.
 4. A dredging apparatus as set forth in claim 1,wherein the drive motor is supplied with energy through a cableextending to a surface of one of a drilling platform and a ship.
 5. Adredging apparatus, comprising:a pumping device driven by a motor, thepumping device having water intake openings and having a pressure end; apipe bend coupled at a first end to the pressure end of the pumpingdevice, the pipe bend having a second end that corresponds to anarrowing outlet end opening for passing water therethrough; an ejectorhaving a first end in which the second end of the pipe bend is disposedin a center portion of said ejector, and a second end that connects toan outlet pipe of the dredging apparatus, wherein said narrowing outletend opening of said ejector maintains a water jet pointed in thedirection of said outlet pipe; and a suction hose coupled to the secondend of the ejector for passing dredging material to the ejector, saidsuction hose connected to said ejector upstream of said water jet andhaving an inlet portion for sucking in material on the seabed andtransferring said material to said center portion of said ejectorupstream of said water jet, and wherein said suction hose, said ejectorand said outlet pipe form a substantially continuous bore.
 6. Thedredging apparatus according to claim 5, wherein the ejector has agradually increasing pipe diameter in a direction from a middle portionof the ejector to the second end of the ejector.